1. Field of the Invention
The present invention relates to a safety device for mounting on an automatically operated garage door and responsive to engagement with an object to deactuate and reverse an operator.
2. Description of the Prior Art
The advent of automatic doors actuated by automatic operators has led to the need for pressure sensitive deactuation devices which are responsive to contact with an object located in the door path to deactuate the operator. A number of injuries, and even deaths, have been reported due to the lack of an effective safety actuator for stopping or reversing an automatic operator upon the door making contact with a hapless person passing through the path thereof.
Current popularity of overhead garage doors driven by an automatic operator for opening and closing have led to further development of various sensing devices. Many such automatic closures incorporate a pressure sensing arrangement along the lower edge of the door such that upon contact with a vehicle or the like will deactuate the operator to minimize damage to the vehicle or door structure. However, such devices typically suffer the shortcoming that the deactuating devices require application of significant amounts of force thus resulting in the impact of damaging forces to the vehicle before the deactuator becomes fully operative.
U.S. Pat. No. 3,001,038 to Gazelle recognized the existence of a need for an automatic deactuator highly responsive to the encountering of an obstruction to halt closure. However, the relatively sophisticated and expensive pistons for carrying the moveable edge has proven unduly expensive to fabricate and does not afford the necessary angular range for application of actuating forces for practical use on a one-piece overhead garage door.
Thus, there exists a need for a deactuator which is highly sensitive to contact with an object during closure of the door such that contact with a small child or the like during closure will deactuate the closure to protect the child from injury. The design challenges for such a device are greater for one-piece overhead garage doors since those doors typically close in a manner which swings the free lower end of the door through an arcuate path. This results in contact being made by the lower edge of the door with an obstructing object from any one of a number of different directions throughout a wide range of angles depending on the height of such lower edge at the point of contact.
Prior efforts to devise satisfactory deactuation mechanisms have led to the proposal of a symmetrically shaped semicircular hollow deflectable channel member mounted centrally on a door edge and carrying an electrical contact and which will be deflected upon impact to engage a cooperating contact to thereby generate an electrical signal. A device of this type is shown in U.S Pat. No. 1,511,055 to Entwistle. Devices of this type, while satisfactory for their intended uses, suffer the shortcoming that substantial force is required for deflection of the channel and contact with an object at an angle of, for instance, 45.degree. to the plane of the door, typically fails to adequately deflect the channel to make contact and close the circuit.
Other efforts to provide a satisfactorily sensitive door edge sensing mechanism has led to the proposal of pneumatic tubes or the like mounted adjacent the door edge for deformation upon contact to increase the pressure in the tube for sensing by a pressure sensitive switch. A device of this type is shown in U.S. Pat. Nos. 3,303,303 and 4,620,072 to Miller. Such devices, while sufficiently sensitive to be actuated upon engagement of the door edge with a forklift vehicle or the like, typically cannot be designed sufficiently sensitive to respond at different temperatures, under a variety of climatic conditions, and with sufficient sensitivity to fully minimize injury to a person contacted thereby.
Other solutions have been proposed which incorporate electrically conductive strips spaced apart by means of a compressible insulative strip or the like to create a pressure sensitive switch such that compression thereof permits the contacts to come into engagement with one another to thereby generate an electrical signal. Devices of this type are shown in U.S. Pat. Nos. 2,843,690, 3,133,167, 3,855,733, 4,273,974, 4,349,710, 4,396,814, 4,785,143, 4,908,483 and 4,920,243 to Miller. Devices of this general type have been marketed under the trade designation Miller Edge by Miller Edge, Concord Industrial Park, Concordville, Pa. 19331. Such devices, while satisfactory for commercial installations where cost is not of particular consideration, have limited application for use on the free edge of one-piece garage doors since such devices must be capable of mass production and economical to use.
Other efforts to produce a satisfactory device have led to the proposal of spaced apart conductive strips housed in a flexible channel mounted centrally on a door edge and designed with an internal strut work such that forces applied to the channel is intended to act through such struts to press the strips together. Devices of this type are shown in U.S. Pat. No. 3,118,984 to Koenig and U.S. Pat. No. 4,115,952 to French. The cost of such continuous strips is considerable and range of angles from which actuation forces may be applied is limited.
Devices have also been proposed which incorporate hollow tubes mounted along the edges of automatic doors for containing pressurized fluid which is responsive to application of forces for deactuating an operator. A device of this is shown in U.S. Pat. No. 4,133,365 to Schleicher. Such devices, while satisfactory for installations where the climatic conditions are constant and substantial forces are not objectionable, suffer the shortcoming that such fluid does not typically operate over wide ranges of temperature variations.
Thus, there exists a need for an actuator apparatus for mounting on the lower edge of a one-piece garage door and configured such that application of forces thereto from various different angles as dictated by the point in the path followed by the lower edge during closure at which contact is made with an obstruction to thereby avoid application of excessive forces to the object.